Soybean South April 2024

EPA Gives Update on Over-the-Top Uses of Dicamba

On Feb. 14, 2024, EPA issued an Existing Stocks Order for Dicamba Products Previously Registered for Over-theTop Use on Dicamba-Tolerant Cotton and Soybean. This Order addresses use of the formerly registered dicamba products and authorizes limited sale and distribution of dicamba products that are already in the possession of growers or in the channels of trade and outside the control of the pesticide companies.

Background

Dicamba is an herbicide used to target broadleaf weeds in agricultural and non-agricultural settings. The herbicide is registered for use at specified stages in agricultural crop fields of corn, cotton, sorghum, soybeans, sugarcane, and other crops. The dicamba products subject to the February 2024 vacatur were registered to be sprayed OTT of genetically engineered dicamba-tolerant soybeans and cotton after the crops have emerged from the ground. There are also dicamba products that are only registered for non-OTT applications. These products are applied earlier in the growing season before crop emergence while OTT products can be applied later in the growing season after crop emergence.

Dicamba was first registered for OTT uses on dicamba-tolerant cotton and soybeans in 2016. In 2017 and again in 2018, EPA amended the registrations of all OTT dicamba products following reports that growers had experienced crop damage and economic losses resulting from the off-site movement of dicamba. The U.S. Court of Appeals for the Ninth Circuit vacated the 2018 registrations in June 2020 on the basis that “EPA substantially understated risks that it acknowledged and failed entirely to acknowledge other risks.” Days after the court’s decision, EPA issued an order for the affected products that addressed existing stocks.

In October 2020, EPA issued new registrations for two dicamba products and extended the registration of an additional dicamba product until 2025. All three registrations included new measures that the Agency expected to prevent off-target movement and damage to non-target crops and other plants. Further state-specific amendments to the registrations occurred in 2022 and 2023.

In response to a lawsuit against EPA concerning these registrations, on Feb. 6, 2024, a ruling by the U.S. District Court of Arizona vacated the 2020 registrations for OTT dicamba products XtendiMax, Engenia, and Tavium. As of Feb. 6, 2024, these products are unregistered, and sale or distribution of these products is unlawful except as provided in EPA’s February 2024 existing stocks order.

Existing Stocks Order

EPA has issued an Existing Stocks Order to allow for limited sale and distribution of dicamba OTT products that were already in the possession of growers or in the channels of trade and outside the control of pesticide companies as of Feb. 6, 2024. The order also prohibits the use of these dicamba products except where the use is consistent with the previously approved labeling, which included

measures intended to reduce environmental damage caused by offsite movement of the pesticide.

This Existing Stocks Order is limited in time and scope, allowing for certain sale, distribution, and use of existing stocks of these formerly registered dicamba products for the 2024 growing season. EPA has received ample evidence that millions of gallons of OTT dicamba had already entered the channels of trade prior to Feb. 6, 2024. Additionally, most growers have already placed orders for dicamba-tolerant seed for the 2024 growing season and, given the timing of these registrations being vacated, are not able to pivot to another herbicide-tolerant seed and herbicide system.

The issuance of this Existing Stocks Order will help ensure that growers who already possess OTT dicamba and/or have already purchased dicamba-tolerant seeds and thus are reliant on the availability of specific products solely for the 2024 growing season: (1) apply only dicamba formulations designed for use over the top of dicamba-tolerant soybean and cotton, rather than violating FIFRA by misusing more volatile dicamba formulations, which could lead to greater offsite movement (and thus potential damage to non-dicamba tolerant crops and other plants); and (2) apply these OTT dicamba products consistent with restrictions intended to reduce offsite movement and protect human health and the environment. Thus, it is necessary for EPA to issue an Existing Stocks Order to ensure that growers follow these directions for use, which were designed to reduce environmental damage caused by offsite movement.

Under this order, end users of existing stocks may only use the formerly registered products consistent with the previously approved labeling for the products and must stop use of these products by the relevant dates laid out in the Order.

For more information, visit https://www.epa.gov/pesticides/ dicamba.

This article is provided by the Environmental Protection Agency.

Herbicide Drift Study Provides New Recommendations for Aerial Applications

Soybeans o er a potential late-season food source for pollinators but are sensitive to damage from herbicide dri , or when an herbicide moves away from its intended target. Researchers with the Arkansas Agricultural Experiment Station conducted a study to determine the e ects of spray dri from ground and air-based applications.

e study validated U.S. Environmental Protection Agency herbicide dri prediction models and provides recommendations for aerial applications of Loyant. e researchers estimate that implementation of the mitigation strategies recommended by this research could save nearly $2 million each year for Arkansas growers and applicators.

The Problem

Herbicide “dri ” occurs when the wind carries an herbicide application o target and causes unintended damage to a nearby crop. In Arkansas alone, an average of 400 dri complaints have been led with the Arkansas State Plant Board each year since 2018.

e herbicide Loyant, which is commonly used on rice elds to control barnyardgrass, sedges, and pigweed, can cause harm to neighboring soybean crops.

When soybean plants are damaged by herbicide dri , the negative e ects go beyond the plants themselves. Although self-pollinating, soybean plants o er a pollinator-foraging source late in the season.

The Work

A study on ground and air applications of the herbicide Loyant was conducted at the Rice Research and Extension Center in Stuttgart by Tommy Butts, researcher with the Arkansas Agricultural Experiment Station and Extension weed scientist with the Arkansas Cooperative Extension Service.

Tommy Butts

For the ground-based applications, researchers used a Case 5550 AimPoint tractor with a 100-foot boom, set three feet above the ground, driving 20 miles per hour across the test area. For aerial applications, they used an AirTractor 802A with a 72-foot swath width. e plane ew an average of 15 feet above the ground with an average airspeed of 145 miles per hour.

Researchers conducted 10 spray passes with both application

methods while in an average eight miles per hour crosswind. e impacts of herbicide dri were measured using water-sensitive cards and by evaluating the e ects on soybean reproductive structures.

The Results

Results from the research indicated that aerial applications had an increase in downwind spray dri of about three- to ve-fold compared to the ground application across all data collected.

Researchers found that soybean reproductive structures were reduced by 25% up to 100 feet downwind from a ground-based application. Dri from aerial applications damaged nearly 100% of soybean reproductive structures at 200 feet downwind.

Based on their research, Butts and co-authors of the study recommend that aerial applicators use a “coarse” droplet size and make three to ve complete upwind swath width adjustments to reduce spray dri potential.

Dri mitigation recommendations for both application methods also include dri reduction adjuvants, reduced boom and ight heights, and applying when the wind direction is more favorable, blowing away from sensitive areas.

The Value

Butts said a better understanding of application dri potential and implementation of the mitigation strategies recommended by this research could save nearly $2 million each year for Arkansas growers and applicators. He estimates a corresponding potential for reducing dri complaints by 50%.

Additionally, decreased herbicide dri and damage to soybeans would provide more potential foraging sources for pollinators, which provide critical services to the environment and agriculture.

is article is provided by the Arkansas Agricultural Experiment Station.

This research was supported in part by the following: USDA-ARS Award Nos. 28-6066-9-047 and 58-3091-1-015, checko funds distributed by the Arkansas Soybean Promotion Board. Additional assistance provided by the Tri-County Farmers Associates and Cole Hartley of Hartley Flying Service.

Research Leads to Potential Increases in Missouri Soybean Yield

By Linda Geist

Missouri soybean yields have the potential to reach or exceed national averages, says University of Missouri Extension state soybean specialist Andre Reis.

Nationally, soybean yields have grown at a pace of 0.4 bushel per acre per year over the past 80 years, according to the USDA National Agricultural Statistics Service. Illinois growers saw a 0.47 bushel per acre per yield upturn, while Iowa boasted a 0.48 bushel per acre per year increase.

By contrast, Missouri yields fell behind, with an average increase of only 0.375 bushel per acre per year. Reis hopes to change that by providing growers with science-based research from MU to boost yields and farm income of soybean – the state’s No. 1 crop in acres and value.

Soybean production in Missouri is divided regionally into seven districts. Of those, yields in Districts 6 and 7, which comprise counties that run from the St. Louis area to the Missouri Bootheel, rose above the rest of the state. District 7 jumped to a 0.62 bushel per acre increase in 2020.

Even within the districts, some areas showed standout performances, including Atchison, Lafayette, Miller, St. Francois and Butler counties. Pockets of District 1 in northwestern Missouri also fared well above the statewide average.

Several factors may play a part in areas where yields increased significantly, says Reis. Some farmers may adopt new technologies and strategies quicker than others. Reis says an example of this is adopting optimal planting dates, adjusting plant population according to variety requirements and enhancing soil fertility and crop protection management. In non-irrigated areas, strategies to avoid drought include combining maturity groups and planting dates to decouple pod setting and seed-filling periods from the hottest and driest periods of the season.

Overall, each of the seven districts saw the biggest yield jumps since the period of 1971-1996.

Reis’ work confirms previous MU research showing that planting date is one of the best predictors of yield. MU soybean variety test-

ing data from past years shows an average loss of 3.5 bushels per week when planted after May 15.

Weather during soybean’s reproductive stages in July remains the biggest variable influencing yield. Soybean’s long flowering period allows it to withstand some extremes, but extended precipitation shortfalls and high temperatures hinder growth during this critical stage.

Reis has analyzed years of data from the MU Variety Testing Program and found that certain maturity groups produced significantly higher yields than others in all environments. The variety testing program has collected data at Missouri test plots throughout the state since 1973. Researchers note crop management practices and soil and water conditions in the results.

Maturity Group IV plantings saw a yield

increase of only 0.29 bushel per acre per year, while Maturity Groups II and III saw upturns of 0.34 bushel per acre. See https:// varietytesting.missouri.edu/soybean/ for more.

Reis developed a maturity group decision tree to help growers decide which maturity group to choose. The tree considers day length, seasonal potential evapotranspiration rate, preseason precipitation, precipitation during the early vegetative state, day length during flowering and other factors. The decision-making tool is available by request from Reis.

Illinois and Iowa soybean yields outpaced Missouri by 0.10 and 0.11 per acre during the same period. Kansas lagged slightly behind Missouri with 0.02 less bushels per acre.

For more information, contact Reis at areis@missouri.edu or 573-882-4771.

Late-planted soybean benefit from 15-inch rows instead of 30-inch rows. The 15-inch rows allow soybean to capture light, which boosts yield.

PHOTO COURTESY OF ANDRE REIS/UNIVERSITY OF MISSOURI